Optical fiber connectors are an essential part of practically all optical fiber communication systems. For instance, such connectors are used to join segments of fiber into longer lengths, to connect fiber to active devices such as radiation sources, detectors and repeaters, and to connect fiber to passive devices such as switches and attenuators. The principal function of an optical fiber connector is to optically couple a fiber with the mating device (e.g., another fiber, an active device or a passive device) by holding the end of the fiber, typically in a ferrule, such that the core of the fiber is axially aligned with the optical pathway of the mating device.
The operation of fiber optical connectors may be classified as either pull-proof or non pull-proof. Referring to FIG. 4, a pull-proof connector 401 and a non pull-proof connector 402 are shown. These particular connectors are SC type connectors, which is a common and well known optical connector type. Each connector is configured to terminate an optical cable. An optical cable comprises an optical fiber, a jacket covering the fiber, and possibly strength members (aramide fibers) between the fiber and the jacket.
With respect to the pull-proof connector 401, when a cable is terminated to it, the cable's jacket (and its strength members, if any) is secured to the rear body 405 of the connector, which, in turn, is attached to the housing 406. Accordingly, if a tensile load T is applied to the cable, the load will be transferred from the cable's jacket, to the rear body 405, and then to the housing 406. The load is therefore not transferred to the ferrule assembly 403. Accordingly, when the connector is mated, the ferrule assembly will not be affected (i.e., drawn back) by the tensile load, and thus the ferrule end face 403a will continue to make contact with the optical pathway of the mating device.
With respect to the non pull-proof connector 402, when a cable is terminated to it, the cable jacket is secured to the rear portion 407 of the ferrule assembly. Unlike the rear body 405, the rear portion 407 is not anchored to the housing 406, but rather is essentially integral with the ferrule assembly. Accordingly, when a tensile load T is applied to the cable, the load on the jacket is transferred to the rear portion 407 and directly to the ferrule assembly 404. This causes the ferrule end face 404a to separate from the mating device, thereby disrupting the optical coupling.
Therefore, a pull-proof connector continues to maintain optical connection at ferrule end face 403a when a tensile load is applied to the cable, while a non pull-proof connector will allow the ferrule end face 404a to separate from the optical coupling when a tensile load is applied to the cable. For this reason, pull-proof connectors are preferred over non pull-proof connectors in ordinary applications.
Although pull-proof connectors are generally preferred, Applicants have discovered that variations in cable types in the field can undermine the benefit of a pull-proof connector. Specifically, the standard LC-type and SC-type pull-proof connectors are designed to terminate loose construction cable where the buffer optical fiber is free to move inside the outer cable jacket. Specifically, referring back to FIG. 4, in a pull-proof connector, when a mating force is applied to the ferrule end face 403a, the ferrule assembly 403 moves backward, causing the buffered fiber to move backward relative to the jacket which, as mentioned above, is anchored to rear body 405.
This mechanism becomes problematic, however, for tight-jacketed cables. A tight-jacketed cable does not allow the optical fiber to move independently of the jacket. Consequently, when a mating force M is applied to ferrule end face 403a, the ferrule assembly 403 moves backward despite the jacket being anchored to the rear body 405. Because the fiber cannot move back within the jacket, the fiber is compressed between the ferrule end face 403a and the rear body 405.
Referring to FIG. 5, an LC connector is shown terminating a tight-jacketed cable. As the connector is mated to the adapter 502, a mating force is imparted on the connector's ferrule end face (not shown), which compresses the fiber as mentioned above and causes a micro bend 503 in the fiber. Such micro bends are known to diminish connector performance or fracture the fiber. Therefore, pull-proof connectors can have a detrimental effect if used to terminate tight-jacketed cables.
The impact of different cables on basic connector function highlights the importance of compatibility during system design. Unfortunately, Applicants have observed that there is a general lack of control over the type of cables being used in optical networks. Indeed, tight-jacketed cable is often used on site without the installer's knowledge of detrimental effects. As the use of tight-jacket cable becomes more prevalent, the lack of industry standards coupled with user ignorance will increase the occurrence of incompatibility between the cable and the connector. Micro bend failures, fiber breakage, and the list of long term reliability issues are the resulting outcome.
Because the occurrence of tight-jacketed cable in the field is often difficult to predict and control, there is a need for flexibility in connector choices in the field. Specifically, technicians need to be able to install either a pull-proof field installable connector or a non pull-proof connector in the field depending upon the cable available. The present invention fulfills this need among others.